Coix lacryma-jobi L. (Jobstears)

Geographic Distribution and Importance

Jobstears (Coix lacryma-jobi) belongs to the Gramineae and is a diploid species (2n = 20). It is widely distributed in the temperate zones in the world, especially in humid areas of low latitude. In China, it is mainly distributed in the south provinces and there are wild and cultivated types of jobstears. Jobstears is a perennial root species and has strong root system with thick fibrous roots (3 mm in diameter). The stem is straight, 1 -1.5 m high and has ten nodes and some branches. The leaf is conifer-shaped and 30 cm in length and 1.5-3 cm in width, midrib thick and prominent. Unisexual flower, monoexism and axillary or top-growing raceme. Female spikelets are at the base of inflorescence and male spikelets at the top of the inflorescence. The blooming period is July-September and in September-October the grains ripen.

The fruit of jobstears is oval with a hard outer shell. The endosperm and embryo of the fruit is called “Job’s tears” and are utilized for both food and medicine. The nutritive value of Jobstears is primarily as a cereal crop and the kernel is reputed to be “the king of cereals”. Jobstears is also a highly waterlogging-, drought- and salt-tolerant and high-productive crop. It is worth developing this dual-purpose plant with nutritive value, hygienic role, high yield and stress tolerance for food and medicine.

Propagation Method and Medical Application

Jobstears is usually an annual seed-propagated plant. In warm areas it can also be perennial herbaceous. Its kernel contains 13.7%-17.6% protein (compared to 6.5%-6.9% in rice), 11.74% lipid (compared to 0.2%-0.8% in rice), and 67.35% starch, most of which is water-soluble and easily absorbed and digested. It also contains P, Fe, Ca, vitamin B1 and amino acids such as leucine, arginine, lysine and tyrosine. Jobstears leaf contains an alkaloid whose chemical structure is unknown. The liposoluble part of jobstears contains coixenolide (C38H70O4) and coixol (C8H7O3N). Pharmacological examinations indicate that: (1) Coixenolide can inhibit ascite cancer cell growth; (2) in vitro, a low concentration of coixenolide increases tension of the intestinal wall of rabbit; (3) coixenolide increases uterine tension in rabbit and guinea pig; (4) coixenolide in vitro reduces convulsion of frog muscle; (5) coixol and fatty acid with more than 12 carbon atoms reduce the calcium content of blood serum and blood sugar; (6) coixol allays fever, and eases pain in white mice and white rats.

Root of jobstears can be used for relieving endogenous fever and dampness with diuretics and expelling roundworm. The mytonin in jobstears root can be used for reducing inflammation, easing pain, stimulating muscle movement and inhibiting growth of cancer cells.

Jobstears: Conclusion and Prospects

Jobstears is not only a healthy food with high nutritive value but an effective inhibitor to growth of cancer cells, and the demand for this traditional Chinese health food is now increasing. There has been not enough research work in variety improvement of jobstears, although there are some agronomic characters to be improved. Success in tissue culture of jobstears offers an efficient biotechnique for variety improvement. It also offers a potential tool for mass production of effective medicinal compounds such as coixenolide, coixol and mytonin through cell suspension culture.

For somatic tissue culture, callus can be induced from 1-cm-long inflorescences on N6 medium with 2mg/l 2,4-D and 3%-5% sucrose. Plants can be regenerated when callus is transferred to MS medium with 0.5mg/l kin and 0.01 mg/1 NAA.

Pollen at the mid-late, uninuclear stage is ideal for anther culture. Pretreated with 0.8 M sucrose for lOmin followed by culturing on the N6 medium with 2 mg/1 2,4-D 3%-6% sucrose callus or pollen embryos can be easily induced. Haploid plants can be regenerated after the callus or embryos are transferred to N6 medium with 1 -2 mg/1 kin and 0.5 mg/1 IAA. The optimum temperature for both inflorescence and anther culture is 25-28°C. Photoperiod is 16 h light.